This invention relates to decoding of television signals, and particularly to separation of chrominance and luminance in such decoding.
Separation of chrominance (chroma) and luminance (luma) in conventional television transmissions (e.g., NTSC, PAL, SECAM) is not an easy task because the two signals share spectrum. Typically, the separation is performed using one or two-dimensional bandpass filtering.
When film material, which is recorded at 24 frames/second, is converted for television transmission, which uses different rates (e.g., 30 frames/second, or 60 fields/second, for NTSC), it is conventional to generate successive fields of the television signal from the same frame of the film material. In the case of NTSC transmission, the conventional conversion technique is known as "3-2 pull-down"; each pair of film frames is transformed to five NTSC fields; three NTSC fields are generated from one film frame, and two from the other.